This invention pertains to fuel cell systems and, in particular, to fuel cell systems useful in mobile applications.
Recently, considerable interest has been expressed in the development of fuel cell systems for mobile applications. One prime goal in the design of fuel cell systems of this type is to realize systems which are as light as possible. Light-weight fuel cell systems, however, are difficult to realize following customary design principles.
More particularly, fuel cells generate electricity through galvanic combustion of fuel process gas with oxidant process gas. Typically, the oxidant process gas is air which can be obtained from the fuel cell environment with little, if any, processing. The fuel process gas, on the other hand, is usually hydrogen and its generation requires processing in the form of carbon conversion via cracking, partial oxidation or steam reforming or a combination of these reactions such as autothermal reforming. To obtain maximum hydrogen from hydrocarbon, the most suitable of these techniques is steam reforming. Steam reforming, however, requires water which must be obtained either from a water supply or by recovery of the water produced by the fuel cell during operation. With large scale stationary systems obtaining such water presents no significant problem, as there is usually available a water supply and/or heat exchange equipment for water recovery. However, in systems for mobile use, the excessive weight of the required heat exchange equipment makes the use of such equipment impractical. Most mobile type systems have, thus, turned to carrying a portable water supply which adds to the weight of the system, but to a lesser degree than conventional heat exchange equipment. In these systems the water from the portable supply is added to the hydrocarbon fuel which is then steam reformed to produce the hydrogen fuel process gas. Methanol and ethanol are attractive fuels for this purpose, since they can be converted by steam reforming to hydrogen at relatively low temperatures.
While the above-described systems utilizing a portable water supply can be employed, lighter weight portable systems are still being sought.
It is a primary object of the present invention to provide a fuel cell system which can be advantageously used in mobile applications.
It is a further object of the present invention to provide a fuel cell system which can be of lighter weight than presently contemplated systems.